Slides in this set

Slide 1

Slide 2

THERMAL RADIATION Thermal radiation is the transfer of heat by infra-red waves, which are part of the electromagnetic spectrum. All objects emit heat radiation The hotter an object, the more heat radiation it gives off. Heat radiation passes through a vacuum, this is how we get our heat from the sun. The transfer of heat radiation does not involve particles.…read more

Slide 3

SURFACES AND RADIATION Dark, matt surfaces are good absorbers of radiation, so they will get hotter if left out in the sun than a shiny white surface. However they are also good emitters, and they will lose heat quicker than a shiny white surface.…read more

Slide 4

CONDUCTION Conduction is the transfer of heat through a substance , usually a solid, gases and liquids are poor conductors of heat. When one end of a metal is heated, then those end particles gain kinetic energy and they vibrate each other and gain more energy. Metals also have delocalised (free) electrons, which vibrate throughout the metal and pass on their energy. Poor conductors are called insulators. Good insulators have pockets of air to trap heat in, for example air pockets in fibreglass.…read more

Slide 5

CONVECTION Convection occurs in fluids, that is liquids and gases. When a fluid is heated it expands and becomes less dense, due to this lower density, it rises and it is replaced by cooler fluid. This process repeats and you get what are called convection currents.…read more

Slide 6

HEAT TRANSFER BY DESIGN Heat transfer by conduction can be reduced by using insulators Heat transfer by convection can be reduced by preventing convection currents from forming, for example trapping air in pockets. Heat transfer by radiation can be reduced by using light shiny surfaces. The converse can be applied to maximise heat loss to keep things cool.…read more

Slides in this set

Slide 1

Slide 2

THERMAL RADIATION Thermal radiation is the transfer of heat by infra-red waves, which are part of the electromagnetic spectrum. All objects emit heat radiation The hotter an object, the more heat radiation it gives off. Heat radiation passes through a vacuum, this is how we get our heat from the sun. The transfer of heat radiation does not involve particles.…read more

Slide 3

SURFACES AND RADIATION Dark, matt surfaces are good absorbers of radiation, so they will get hotter if left out in the sun than a shiny white surface. However they are also good emitters, and they will lose heat quicker than a shiny white surface.…read more

Slide 4

CONDUCTION Conduction is the transfer of heat through a substance , usually a solid, gases and liquids are poor conductors of heat. When one end of a metal is heated, then those end particles gain kinetic energy and they vibrate each other and gain more energy. Metals also have delocalised (free) electrons, which vibrate throughout the metal and pass on their energy. Poor conductors are called insulators. Good insulators have pockets of air to trap heat in, for example air pockets in fibreglass.…read more

Slide 5

CONVECTION Convection occurs in fluids, that is liquids and gases. When a fluid is heated it expands and becomes less dense, due to this lower density, it rises and it is replaced by cooler fluid. This process repeats and you get what are called convection currents.…read more

Slide 6

HEAT TRANSFER BY DESIGN Heat transfer by conduction can be reduced by using insulators Heat transfer by convection can be reduced by preventing convection currents from forming, for example trapping air in pockets. Heat transfer by radiation can be reduced by using light shiny surfaces. The converse can be applied to maximise heat loss to keep things cool.…read more